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Underground column of molten rock found at
Yellowstone
Research suggests activity is fueling Pacific Northwest's volcanic activity
beneath the planet's crust.
The very existence of such mantle plumes is
doubted by some scientists.
UC, Berkeley / Keck Caves, UC, Davis
New high -resolution tomographic images show there is a continuous, whole -mantle plume
beneath the Yellowstone Snake River Plain.
By Lynne Peeples
OurAmazingPlanet
updated 9/8/2010 10:58:09 AM ET
A plume of molten rock rising from deep
beneath Yellowstone National Park is probably
what is fueling the region's volcanic activity, as
well as tectonic plate oddities across the
Pacific Northwest, new research suggests.
Building on a growing body of evidence,
Mathias Obrebski of the University of
California, Berkeley, and his colleagues
created the most convincing picture to date of
a Yellowstone mantle plume — one that
extends from about 621 miles below the
surface of the Earth.
"They are extraordinary features, in size and in
the fact that they travel upward through the
whole mantle in solid form," said Vic Camp of
San Diego State University, who was not
involved in the new study. "It's a really simple
idea to explain a number of different
phenomena on Earth. But the simple idea was
very difficult to test."
"Chemical and physical volcanology evidence
suggested a plume, but this is the first seismic
proof," Camp told OurAmazingPlanet.
Obrebski's team used data from a new, dense
deployment of seismometers, called the
Earthscope USArray, to get a high-resolution
image of the once-elusive mantle, along with
information on the unusual structure of the
subducting Juan de Fuca slab to its west. The
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Debates have long been waged over whether
erupting and shaking in the area over the last
few millions of years — and a track marked
out by a chain of volcanic calderas along the
Yellowstone Snake River Plain in Idaho —
could be the work of a column of hot rock
rising up from deep within the Earth's mantle .
The mantle is the layer of hot, viscous rock
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Juan de Fuca plate is a small tectonic plate
jammed in between the much larger Pacific
and North American plates.
Much like an MRI scan of a human body,
seismometers' antennas capture seismic
waves of earthquakes traveling through the
earth from various directions. The waves'
speeds provide hints of the materials and
temperatures they pass through, informing the r
esulting 3-D image, explained Robert Smith of
the University of Utah, who wasn't involved in
the new research but whose group had
recently imaged Yellowstone's mantle plume
down to about 372 miles (600 km).
2/15/11 2:17 PM
that a few may have been associated with
eruptions from mantle plumes."
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The plume is thought to be more or less
stationary, with the North American plate —
and the Juan de Fuca subducting beneath it —
slowly sliding southwesterly over the plume.
So what is now Oregon probably sat where
Yellowstone is today about 17 million years
ago, baking and breaking over a hot plume of
rock, Camp said.
Obrebski said in an interview: "There's been
subduction in the [Oregon] region for more
than 150 million years, so we'd expect to see a
large continuous slab. But what we see are
just fragments."
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The location of those pieces, he added,
suggests that the slab and the plume are
tightly related.
The findings were detailed in the July 22
edition of the journal Geophysical Research
Letters.
These observations may also help explain the
unusual lack of deep seismology in the Pacific
Northwest, and perhaps shed light on some
larger mysteries. "If you look at the mass
extinctions on Earth," Camp said, "we think
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